As an important part of a motor train, a motor train underframe is mainly formed by the auxiliary machining of a motor train underframe tool. Presently, the structure of the motor train underframe tool for the auxiliary machining of the motor train underframe is large in volume, so that the motor train underframe tool is not convenient for transportation and movement; and the adjustability thereof is not good and not capable of meeting the requirements of the auxiliary machining machining of the motor train underframes with different types.